Understanding multiphase flows is vital to solving the most pressing human
problems: clean air, clean water and the sustainable production of food and
energy. Here we will focus on a subset of multiphase flows involving
non-deforming particles in a carrier fluid: particle suspensions over a wide
range of particle-to-fluid density ratios, ranging from solid particles in a
gas (high density ratio) to buoyant particles that approximate small bubbles
in a contaminated liquid (low density ratio). We will see that hydrodynamics
and heat transfer in these flows result in rich multiscale physics, such as
clustering and pseudo-turbulence, with important practical implications. As
we attempt to explain and predict these phenomena we will encounter the
peculiar challenges that multiphase flows pose for standard statistical
mechanics. The need to build accurate closure models for unclosed terms that
arise in statistical theories motivates the development of particle-resolved
direct numerical simulations (PR-DNS). PR-DNS can be used to discover new
multiphase flow physics and develop models. Selected results will highlight
recent progress and the talk will conclude with an outline of challenges
that lie ahead.
[Preview Abstract]